#include <bits/stdc++.h>
using namespace std;

double n;

double solve(){
    if(n == 0) return 0;
    double l, r;

    if(n > 0) l = 0, r = max(1.0, n);
    else l = min(-1.0, n), r = 0;

    while(r - l > 1e-8){
        double mid = l + (r - l) / 2;
        double cube = mid * mid * mid
        if(cube >= n) r = mid;
        else l = mid;
    }
    return l;
    
}
int main(){

    cin >> n;
    double x = solve();
    cout << setprecision(6) << x << '\n';
    return 0;
}